With the rapid development of thin film transistor liquid crystal displays, the dimension of a liquid crystal display can be getting larger and larger. Consequently, it happens in an exposure process that the size of the pattern on a single large-size glass substrate is larger than that of a photo mask. Under this circumstance, it is necessary to device the pattern of the photo mask into a plurality of portions for multiple exposure operations on the single large-size glass substrate. The plurality of portions of photo mask pattern are then joined to construct the pattern on the single large-size glass substrate.
FIG. 1 through FIG. 3, for example, are schematic diagrams illustrating the combination and exposure on a single large-size glass substrate with a plurality of portions of photo mask according to prior art. As shown, two portions of photo mask are used, wherein each of the photo mask portions include an active area (Area A or Area B) and an inactive area (Area A′ or Area B′). In the inactive area, alignment precision measurement and check marks (total pitch marks), which are shown as small blocks in the figures, are provided for measuring deflection or deformation level of the pattern on the substrate having been subjected to exposure, compared with the pattern in original design. As two exposure operations are conducted on the glass substrate 9 with two photo mask portions, a stitching exposure region 90 would appear. Since the stitching exposure region is in the active area, and the total pitch mark is much larger than a pixel in the active area, for each of the two exposed regions subjected to two exposure and jointing operations, no total pitch mark can be defined at the side of the stitching exposure region. As such, no alignment precision information can be measured for each of the two exposed regions at the side of the stitching exposure region, so the pattern deflection and deformation level cannot be monitored herein. Thus the TFT array substrate might misalign with the color filter substrate, and defects, e.g. light leakage problem, of the LCD might occur.